Flexible, profiled hollow cylinders play a major role in many areas of technology. In the automotive industry and in the mechanical and plant engineering and medical technology sectors corrugated tubes are used for protecting and bundling together electrical or other lines and for obtaining flexible connections to peripheral apparatuses. In the electroinstallation field, plastic corrugated tubes are used predominantly as or instead of so-called empty tubes both for outdoor use and, above all, in the walls and ceilings of buildings. Corrugated tubes are used as heat exchangers (when made, for example, of stainless steel in buffer storage units or of plastic for underfloor heating systems). In such applications the corrugated structure is used for increasing the surface area for obtaining maximum heat transfer. Corrugated tube sections (metal bellows) are used for compensating offset axes or for compensating changes in lengths and angles.
Applications WO-A 02/38502, WO-A 02/38191, WO-A 07/096,057 and EP-A 1464342 describe the use of spiral tubes in devices for irradiating liquid media for sterilization purposes.
In many of the abovementioned applications and uses, and in particular in the use of profiled hollow cylinders in irradiation devices, the profiled hollow cylinders are mounted onto cylindrical elements. In WO07/096,057A2, for example, a so-called irradiation module is described which is characterized in that a spiral tube is mounted onto an inner supporting tube in a form-fitting manner. As a result, a channel is formed between the supporting tube and the spiral tube which runs helically from one end of the spiral tube around the supporting tube to the other end of the spiral tube. Such a device is very useful for irradiating fluid media flowing through the channel. For this purpose one or more radiation sources are arranged in the supporting tube and/or around the spiral tube, which irradiate the medium flowing through the channel preferably with UV radiation, and particularly preferably with UVC radiation. The irradiation produces a reduction in microorganisms and/or viruses or a chemical reaction in a photochemical reactor.
The special feature of the perfused channel is the intense, uniform transverse mixing over the entire length of the channel vertically to the main direction of the product flow and a residence time distribution narrowed by turbulent product flow. Transverse mixing guarantees that those fluid layers farther away from the source of radiation, which do not receive any or only a small amount of UV radiation, particularly in the case of highly light-absorbing media, undergo an intense exchange with the UV-radiated layers near the radiation source. This feature and the narrow residence time distribution means that all of the fluid elements undergo a uniform and consistent radiation duration and intensity, which can be adapted to individual requirements by means of the rate of flow and the intensity of the radiation source. The above features guarantee that an effective reduction in microorganisms and/or viruses occurs in the medium. In the case of media which could be damaged by too high a degree of radiation, the risk of the occurrence of too high exposure to radiation and thus partial damage due to an unfavourably broad residence time distribution is effectively reduced.
For this purpose it is however necessary for the spiral tube to surround the supporting tube in a form-fitting manner, thus ensuring that only one single channel is formed which runs helically around the supporting tube. Transverse flows between adjacent channel coils must be avoided, since this would lead to a broadening of the residence time distribution.
In EP-A 1464342 the channel is formed by pulling a spiral tube onto a cylindrical supporting element. By means of a suitable geometry for the spiral tube, which has an inner diameter slightly smaller than that of the supporting element, a tight, form-fitting bond is produced between the two elements. This makes it possible to prevent axial by-pass flows otherwise caused by gaps between the channel coils and the corresponding broadening of the residence time distribution.
The mounting of a flexible, profiled hollow cylinder onto a cylindrical element does, however, represent a technical problem, especially if the smallest inner diameter of the profiled hollow cylinder is smaller than or equally as large as the outer diameter of the cylindrical element.
Due to the profiled contour of its shell, a profiled hollow cylinder has a number of narrow areas (in the present context also referred to as coils) which have to be overcome when mounting it onto a cylindrical element. The mounting process is usually carried out in such a manner that the cylindrical element is pushed into the channel of the profiled hollow cylinder and/or the profiled hollow cylinder is pulled onto the cylindrical element. For each coil in the hollow cylinder which has already been mounted onto the element, an increase in friction occurs between the hollow cylinder and the cylindrical element, so that the force which has to be exerted on the hollow cylinder and/or the element, increases as the length of the hollow cylinder increases.
Depending on the materials used for the hollow cylinder and the cylindrical element the components can become worn, torn or scratched or can even break.
In addition, the process of “pulling” a spiral tube onto a cylindrical supporting element described in EP-A 1464342 for the production of an irradiation device results in indefinite channel geometries. The pulling-on process and the stresses resulting therefrom can have an effect on the spiral geometry. Individual coils can be crushed. Constricted areas in individual channel coils lead to drops in pressure. Due to the crushing of individual channels, gaps between adjacent channel coils can hardly be avoided. This results in a non-reproducible irradiation device with non-specific dimensions. In addition, too high friction can also cause particles to be rubbed off. These particles are critical for various applications, such as for example in the pharmaceutical sector.
The need therefore exists for a method of mounting flexible profiled hollow cylinders onto cylindrical elements which can be carried out easily and keeps the mechanical stresses on the components at such a low level that wear and/or even the destruction of the components cannot take place.
In addition, the need exists for a method of mounting flexible profiled hollow cylinders onto cylindrical elements which can be carried out on an industrial scale.
In particular, the at least partial automatization of the process is of enormous importance in this regard in order, for example, to be able to produce the irradiation devices described in applications WO-A 02/38502, WO-A 02/38191, WO-A 07/096,057 and EP-A 1464342 cost-effectively and reproducibly on an industrial scale.
Based on the known prior art, the object is therefore to provide a method of mounting flexible, profiled hollow cylinders onto cylindrical elements without any of the components being thereby damaged. The method sought should be capable of being at least partially automated. It should be capable of being carried out simply and at low cost. The object is also to provide a device for carrying out the desired method. The device sought should be capable of being operated intuitively and should also be cost-effective.
The method sought should allow the reproducible production of irradiation devices which have well-defined channel geometries and which therefore produce effective and reproducible results in the irradiation of fluid media with electromagnetic radiation, for example for the purpose of inactivating microorganisms and/or viruses by means of UV radiation.
Surprisingly it has been found that flexible, profiled hollow cylinders can be easily mounted onto a cylindrical element if the profiled hollow cylinders are elongated (i.e. axially stretched) along their longitudinal axis.